If you want performance with the TCP/IP communications you should use asynchronous communication. Asynchronous communication means that rather than the HL7 sender sending a message and waiting for an ACKnowledgment message back before sending the next one, the HL7 Sender just keeps sending messages without waiting for the corresponding ACK messages.

	A well-implemented HL7 sender should actually match up the ACK messages it receives for each message to ensure guaranteed delivery. This does not always happen in some poorly written real-world implementations.

The reason asynchronous communication is much faster is because of the 'round-trip' time. If it takes two seconds for a message to be sent over the network and two seconds for ACK to be sent back, the performance of the interface will be no more than 60 * 60 / 4 = 900 messages per hour if you choose to use synchronous communication.

The asynchronous approach removes that limitation. Even though it might take four seconds for an individual message to go through the system, the number of messages going through the system could be much larger.

The next section will consider how the receiver could go about receiving these messages. This deals with the next bottleneck, your persistent queue.